Step aside, Christian Grey — you don’t know what rough sex is unless you’ve made it with a shark.
Yes, those demons of the deep are dastardly in the sack! And if you’re a female shark, you’re definitely getting the raw end of the deal — not to mention the world’s worst hickey.

In honor of Shark Week, we sought the lowdown on their kinky, finny ways from George H. Burgess, director of the Florida program for shark research at the University of Florida and co-author, with Gene Helfman, of “Sharks: The Animal Answer Guide” (Johns Hopkins Press, 2014). What you don’t know will astonish you.

How often do sharks have sex?

As often as possible. Unlike swans, who mate for life, shark sex “happens when it happens,” Burgess says. “It’s like 1 o’clock in the morning, and the bar’s closing.” Male sharks can sniff out ovulating females, who give off pheromones (chemical signals) when they’re ready for mating.

Do the females have any say in the matter?

Nope. Once those signals are out, the female literally has to fend off her suitors: “More times than not, it’s simply the biggest and fastest who gets her. From an evolutionary standpoint, that’s fine, because it assures the fastest animals survive.”

How exactly do they do it?

“Sex with sharks gives new meaning to the expression, ‘It hurts to be in love,’ ” Burgess says. “The poor female is for all intents and purposes raped. Males grab onto the females’ fins and body with their teeth and dig in.” They also have to be athletic, he says, since sex in the water is as frictionless as having sex in space — there’s nothing to hold the bodies in place. That’s where the jaws come in.

Does the female have any protection at all?

Many females of the species — of which there are some 450 — have noticeably thicker skin than their male counterparts. Female sharks are also bigger, “probably so she can take more abuse and carry more young.”

Is it true male sharks have two sex organs?

They’re called claspers — and yes, Burgess says, a male shark has two of them: one on each side of his body. But he uses only one at a time, depending on which side of the female shark he finds himself on. The male inserts his clasper into the female’s cloaca — the urinary/reproductive opening — and deposits his sperm, along with some sea water.

Do sharks have trouble getting and maintaining an erection?

Not at all! “They don’t have to take Viagra,” Burgess says. “They’re ready to go anytime and anyplace.” He says you can tell when a male shark has reached maturity when his clasper, which is made of cartilage, is stiff — “the little guys’ claspers are rubbery.”

How long does the male take to have sex?

“As long as he damn well wants,” Burgess says. But since most sharks do the deed far off at sea, they’re not always observed by scientists, let alone clocked. One exception is the nurse shark, who mates in shallow waters and is often found off the coast of southern Florida and the Caribbean islands. And woe to the poor female of that species, Burgess says: “Multiple males hover around her and even box her in so she has no way out.”

Any take-away tidbit on sharks in utero?

“The sand tiger shark, which gets to be about 12 feet or so, has a really unique reproductive system,” Burgess says. “The first fertilized egg develops and proceeds to eat any other eggs as they come down the fallopian tubes . . . They come out with fully formed teeth because they’ve been munching on their brothers and sisters.”